Small Hydropower Plant with variable speed PM generator

Transcription

1 Witold MAZGAJ, Zbigniew SZULAR, Tomaz WĘGEL, Tadeuz SOBCZYK Politechnika Kakowka, ntytut Elektomechanicznych Pzemian Enegii Small Hydopowe Plant with vaiable peed PM geneato Abtact. Thi pape peent a new concept of a Small Hydopowe Plant SHP) which i baed on a pemanent magnet geneato PM geneato) with a popelle tubine integated with the geneato oto. The PM geneato can wok at a vaiable peed and theefoe enegy poduced by the PM geneato ha to be conveted by mean of a powe electonic unit to fit to the thee-phae powe gid paamete. The pape decibe element of the enegy conveion ytem and it alo peent the eult of numeical calculation of thi ytem woking. Stezczenie. W atykule zapezentowano nową koncepcję Małej Elektowni Wodnej MEW) opatej o zintegowany z tubiną śmigłową geneato ynchoniczny z magneami twałymi. Geneato pacuje ze zmienną pędkością obotową, dlatego enegia pzez niego wytwazana mui być pzekztałcona za pomocą układu enegoelektonicznego do paametów zgodnych z wymaganiami ieci tójfazowej. W atykule opiano elementy ytemu wytwazania i pzekztałcania enegii oaz pzedtawiono pzykładowe wyniki obliczeń numeycznych pacy tego ytemu. Mała Elektownia Wodna z geneatoem z magneami twałymi pacującym ze zmienną pędkością obotową). Keywod: popelle tubine, PM geneato, PWM ectifie, mall hydo powe plant. Słowa kluczowe: tubina śmigłowa, geneato z magneami twałymi, potownik z modulacją zeokości impulów, mała elektownia wodna. ntoduction Small Hydo Powe Plant SHP) ae widely ued aco the wold. Electical geneato fo today mall hydo powe plant ae deigned fo a contant otation peed, which i kept by a peed contolle often coniting of mechanical equipment. Change of enegy povided by wate depend on wate flow, which i vey uneliable fo mall ive in mountainou aea. Theefoe, full efficiency can be achieved fo powe technology with geneato woking at a vaiable peed. So, in thi pape a new olution of a PM geneato integated with a popelle tubine woking at a vaiable peed i dicued [1]. u G i G i u u, ) G i G u, i) Fig.1. Enegy conveion ytem of the Small Hydo Powe Plant t i aumed that the mechanical ytem fo peed contol via the change of the angle of tubine blade i emoved. Thi lead to an eential implification of mechanical ytem but thi in tun equie an application of a powe electonic unit PEU) in the enegy conveion ytem Fig.1). The otation peed of the popelle tubine can be vaiable and fo diffeent value of the wate flow it hould be contolled by the PEU to enue the highet poible efficiency [2]. Due to non-linea tubine chaacteitic it i neceay to fomulate a uitable contol algoithm fo the whole ytem of enegy conveion. Theefoe, the PEU ha to be applied not only to enue the output fequency and voltage equied by the powe gid, but alo to contol the enegy flow fom the PM geneato to the thee-phae gid. Thi pape peent a new concept fo an expeimental powe tation with the vaiable peed PM geneato which i integated with the popelle tubine nominal data of the PM geneato: P N = 30 kw, U N = 500 V, N = 34,7 A, f = 50 Hz, n N = 600 pm). Tubine integated with PM geneato The hydo-et i baed on a tubula tubine contuction whee the woking fluid change peue when it move though the tubine, giving up it enegy. Typical olution utilize a haft to tanfe the toque fom a tubine impelle to a ynchonou o induction geneato. Fig.2. View of tubine integated with PM geneato 282 PRZEGLĄD ELEKTROTECHNCZNY Electical Review), SSN , R. 87 NR 5/2011

2 Thi new contuction avoid the need of a haft and a haft guide ytem. The toque i tanfeed by a pecial extenal ing, being an integated pat of the tubine impelle. Thi ytem i imple, duable and eliable, theefoe it doe not equie pecial evice. Figue 2 how a view of the complete hydo-et deigned by CED [3]. Pemanent magnet ae mounted on the extenal uface of the extenal ing [4] and pace between magnet ae filled with non-magnetic epoxy ein Fig.3). Both the intenal tato uface and the extenal oto uface ae potected by watepoof tube. Wate which flow though the gap between the oto and the tato additionally enue geneato elf-cooling ytem of tato winding and pemanent magnet. Guide vane diect the wate to the tubine vane. The wate flow act on the unne blade Fig.3), cauing unne otation. The guide vane can be adjuted to allow efficient tubine opeation fo a wide ange of wate flow condition and continuou enegy poduction with the highet poible efficiency of the whole ytem. Fig.4. Relation between the PM geneato powe P m and the otation peed ω of the hydo-et fo ome choen guide vane angle α: α 1 = α max = 90 0, α 1 > α 2 > α 3 fo contant head The PM geneato hould be pecially deigned fo the ake of tubine dimenion. t deign hould enue wate potection, pope paamete of thi geneato, epecially it intenal eactance X d and electomotive foce EMF. The mathematical model of the PM geneato which auming the bae-hamonic of MMF and magnetic lineaity i following: 1) L M M L M L M M M M L M in p t) u p 2 m in p t 3) u in p t 4 3) u M L M R M M L R d dt i1 i2 i3 i i R i Fig.3. Location of pemanent magnet on the oto Change of the guide vane angle α can be caued by hydological condition o by a cetain deceaing of enegy conumption in the thee-phae gid. t equie a cetain eduction of the enegy poduction. Thi angle i equal to 90 degee if the guide vane ae fully open and it equal zeo when the hydo-et inlet i cloed. n conequence the contol ytem of the guide vane hould be an integal pat of whole enegy conveion ytem. Figue 4 peent elation P m = fω) between the PM geneato powe and the otation peed of the hydo-et in cae of contant head H whee H i a diffeence between uppe and lowe wate level) fo ome choen angle of the guide vane. The eult of field computation and deign fomula allowed to appoximate PM flux leakage of winding and inductance fo expeimental PM geneato: L = 1,41 mh, M 0,5 L = 0,69 mh, L σ = 0,99 mh, M σ = 0,32 mh, Ψ m = 1,36 Wb, R = 0,99 Ω L d = 3,42 mh, X d = 1,07 Ω. Wate flow and enegy poduction contol ytem The fundamental pupoe of the popoed contol tategy i to tanfe maximum poible amount of enegy, poduced by the hydo-et, to the powe gid. The Enegy Poduction Contolle and Tubine Wate Flow Contolle Fig.5) enue coect opeation of the whole enegy conveion ytem duing change of woking condition. u, ) u, i ) G ig U G, G) U, ) n G n G P m Fig.5. Wate flow and powe poduction contol ytem PRZEGLĄD ELEKTROTECHNCZNY Electical Review), SSN , R. 87 NR 5/

3 The amount of enegy, which can be poduced, depend on hydological condition. The Tubine Wate Flow Contolle decide about the wate team flowing though the tubine by etting pope angle α of guide vane on the bai uppe wate level UWL which hould be contant. The non-linea chaacteitic of the hydo-et tubine integated with PM geneato) hould be toed in a memoy of the Enegy Poduction Contolle and implemented in the contol algoithm. The enegy which can be tanfeed to the thee-phae gid i calculated on the bai of the tubine chaacteitic P m = fω) Fig.4) fo the cuent poition of the guide vane and then, the contolle detemine the efeence cuent fo PEU. Change of net head additionally modify the maximum value of powe on chaacteitic P m = fω) accoding to following fomula: t i neceay to undeline that the guide vane angle α change much lowe with epect to electic quantitie. So, thi angle can be teated a a contant value in the PEU contol ytem. Powe electonic unit PEU) The RMS voltage and the fequency of the PM geneato can change about -60% +30% with epect to the nominal value. t mean that the hydo-et opeate at a vaiable peed. n the popoed enegy conveion ytem enegy poduced by the geneato i conveted into diect cuent enegy DC link), and then it i tanfeed to powe gid 3x400 V, 50 Hz) via voltage ouce invete [5]. n pactice, two cheme of enegy conveion ae ued, epecially with efeence to wind tubine. 2) 3 3/2 P max ) H ) D C F i G i Gm, G m u DC, u G u U DC G u, i G ) Fig.6. Powe electonic unit with the PWM ectifie u, i ) L DC D T DC C F i G u DC i T DC u G U DC m, u u, i ) u, i ) G G Fig.7. Powe electonic unit with the diode ectifie and the DC-DC boot convete n the fit one Fig.6) a PWM ectifie i applied. n thi cae the PM geneato cuent have almot inuoidal hape. The econd one Fig.7) i baed on a diode ectifie and a DC-DC boot convete which can inceae voltage in the DC link. n both cae, the voltage ouce invete i coupled with the powe gid uing a tanfome o induction choke. The econd method of enegy conveion i not ecommended becaue the diode ectifie can caue ignificant ditotion of the geneato cuent with epect to inuoidal hape. A a eult of thi ditotion the geneato toque contain an altenating component with elatively high amplitude [6]. t i a cetain diadvantage becaue the peence of thi altenating component of the geneato toque can badly influence duability and eliability of the hydo-et. PEU contol tategy The main tak of the PEU contol tategy i to deceae the THD facto of the cuent flowing to the thee-phae gid. The tanito of the voltage ouce invete ae contolled accoding to the given inuoidal cuent ignal uing hyteei contolle. The amplitude m of thee ignal i detemined by the powe value which can be tanfeed to the thee-phae gid and by the actual RMS voltage of the powe gid. t i aumed that the phae hift between the given cuent ignal and appopiate phae voltage of the thee-phae gid i almot equal to zeo unity powe facto). The tanito of the PWM ectifie ae contolled imilaly a in the PWM invete. The amplitude Gm of the given cuent ignal hould have a value which pemit to keep voltage in the DC link on the aumed level about 800 V). Thee cuent ignal ae ynchonized with the output voltage of the PM geneato. n geneal, phae hift between voltage and cuent of both convete ae equal to zeo, although, thee hift can be changed. f the RMS voltage of the thee-phae gid achieve the maximum value fo example a a eult of lowe conumption in the powe gid) then the amplitude of the given cuent ignal 284 PRZEGLĄD ELEKTROTECHNCZNY Electical Review), SSN , R. 87 NR 5/2011

4 of the PWM invete deceae. t detemine a cetain change of the guide vane angle α. n thi cae, accoding to the chaacteitic P m = fω) Fig.4), the enegy poduced by the hydo-et i educed. Numeical calculation wee made fo the elected woking cae, which diffe due to changeable hydological condition o due to voltage change in the thee-phae powe gid. Change of hydological condition influence the otational peed of the hydo-et. Theefoe, in numeical calculation it i neceay to take into account the elation between the geneato toque and it otational peed. On the bai of the chaacteitic P m = fω) Fig.4) thi elation can be witten a follow: Figue 9 peent choen wavefom when the guide vane angle α i being changed fom 90 to about 45 degee. n ode to how thi enegy conveion ytem woking it wa aumed that the hydo-et moment of inetia i 15 time lee than the eal value. 3) T m ) Tmax 1 max 2 whee both T max and ω max depend on the guide vane angle α. The choen wavefom in the enegy conveion ytem with the PWM ectifie in a teady tate fo cetain woking condition ae hown in Figue 8. t wa aumed that the guide vane angle α i lee than α max and it wa equal to 30. n thi cae the geneato output powe deceaed to 9 kw. Accoding to the chaacteitic P m = fω), at the optimal woking point, the geneato otate at 432 pm and it voltage and cuent have fequency about 36 Hz. Due to the application of the hyteei contolle the geneato and the PWM invete cuent contain cetain highe hamonic, but the THD facto of thee cuent i lee than 6 pecent. t i woth to undeline that fequencie of the tanito witching in the PWM ectifie and convete ae not contant and they depend on the aumed hyteei width. n the peented cae thee fequencie change between 2 khz and 3 khz. Fig.9. Wavefom in the enegy conveion ytem with the PWM ectifie duing the change of the guide vane angle α: ω geneato otation peed, u DC voltage in the DC link, P out powe given to the thee-phae gid Fig.8. Wavefom in the enegy conveion ytem with the PWM ectifie in teady tate fo α = 30 : u G, i G, T e voltage, cuent and toque of the PM geneato, u inv, i inv voltage and cuent of the PWM voltage ouce invete The maximum enegy amount poduced by the PM geneato deceae if the guide vane angle α i lee than 90 degee accoding to the chaacteitic P m = fω) Fig.4). A hot inceaing of the powe given to the theephae gid hot inceaing of cuent) caue that the geneato achieve the new otation peed value quickly. n the teady tate in new woking condition the guide vane angle α i lee than 90 degee) the cuent amplitude ae lee than peviouly. f the guide vane ae full open again α i equal to 90 degee) then a hot limiting of powe given to the thee-phae gid caue that the geneato otation peed inceae quickly. t i neceay to te that wavefom hape depend on contolle etting in the enegy conveion ytem. The voltage of the thee-phae gid can change ignificantly fate than the guide vane angle. Vey often an inceae of the gid voltage occu when a high-powe PRZEGLĄD ELEKTROTECHNCZNY Electical Review), SSN , R. 87 NR 5/

5 load i tuned off powe conumption in the thee-phae gid i lee than uually). Figue 10 peent the choen wavefom fo thi woking cae. f the gid voltage achieve a given maximum admiible value then the amplitude of the PWM invete cuent ha to be educed. Conequently, the cuent amplitude of the PM geneato ha to be deceaed. At the ame time the guide vane angle α hould be uitably adjuted, due to the ignificant deceae of the enegy tanfeed to the gid, othewie the geneato peed can ie ignificantly. Fig.11. Wavefom in the enegy conveion ytem with the diode ectifie in teady tate: u DCin, u DCout input and output voltage in the DC link epectively, i LDC cuent of choke L DC Fig.10. Wavefom in the enegy conveion ytem with the PWM ectifie duing change of powe conumption in the thee-phae gid t wa ealie emaked that enegy poduced by the PM geneato can be conveted in the powe electonic ytem with the diode ectifie and the DC-DC boot convete. Figue 11 peent choen wavefom in thi enegy conveion ytem fo the ame guide vane angle α a in Figue 8. The geneato cuent ha non-inuoidal hape. t i the eaon that the geneato toque include an altenating component, which ha ignificantly highe value in epect to the enegy conveion ytem with the PWM ectifie. t can ignificantly lowe duability and eliability of the hydo-et. Fig.12. Wavefom in the enegy conveion ytem with the diode ectifie duing the change of the guide vane angle α 286 PRZEGLĄD ELEKTROTECHNCZNY Electical Review), SSN , R. 87 NR 5/2011

6 Duing change of woking condition the enegy conveion ytem with the diode ectifie opeate imilaly to the ytem with PWM ectifie. Figue 12 peent choen wavefom in the enegy conveion ytem with the diode ectifie and the DC-DC boot convete when the guide vane angle α i being changed fom 90 to about 45 degee. Simila wavefom in the ytem with PWM ectifie fo the ame woking condition ae hown in Figue 9. The output voltage of the diode ectifie i inceaed to the aumed input value of the PWM invete. t i neceay to te once again that the geneato toque contain a ignificant altenating component. Concluion The decibed hydo-et ha ome advantage in compaion to claical hydo-geneato with Kaplan tubine. The mechanical pat of that hydo-et i eentially implified becaue a haft doe not exit, a tanmiion gea i not neceay and a blade poition contol ytem i eliminated. All thee fact have ignificant influence on invetment cot and eliability of the whole Small Hydo Powe plant. Unlike enegy conveion ytem in windmill plant the contol algoithm peented in thi pape i elatively imple. The geneato and PWM invete cuent ae diectly haped by mean of hyteei contolle. Thank to thi, the THD facto of thee cuent i atifactoily low. The popoed contol algoithm enue coect opeation of the whole enegy conveion ytem in diffeent woking condition. REFERENCES [1] B i n de A., Schneide T. 2005), Pemanent magnet ynchonou geneato fo egeneative enegy conveion - a uvey, 11th Euopean Confeence on Powe Electonic and Application poceeding, Deden. [2] Koczaa W., Chlodnicki Z., Enet E., Kanodebki A., Seliga R., Bown N.L., Kaminki B, Al-Tayi e J. 2008), Theoy of the adjutable peed geneation ytem, COMPEL: The ntenational Jounal fo Computation and Mathematic in Electical and Electonic Engineeing, Volume: 27, ue: 5, pp [3] Noway Patent No nteget vanntubin og geneato uten nav, owne - TURBNOVA AS, deigne CED p. z o. o. Poland [4] E L - R e f aie A.M., Jahn T.M. 2008), Compaion of ynchonou PM machine type fo wide contant-powe peed ange opeation, COMPEL: The ntenational Jounal fo Computation and Mathematic in Electical and Electonic Engineeing, Volume: 27 ue: 5, pp [5] B a o u di J., Dinavahi V., Knight A. 2007), A eview of powe convete topologie fo wind geneato, Renewable Enegy, No. 32, pp [6] Danilevicz Y., Dozdowki P., Mazgaj W., S o b czyk T., Szula Z. 2005), The influence of failue of a multiphae p.m. ynchonou geneato and a tatic voltage convete ytem on the geneato electomagnetic toque, PoweTech 2005 Confeence poceeding, Sankt. Petebug, pape numbe 520. Autozy: D inż. Witold Mazgaj, [email protected]; Mg inż. Zbigniew Szula, [email protected] D inż. Tomaz Węgiel, [email protected]; Pof. d hab. inż. Tadeuz Sobczyk, [email protected]; Politechnika Kakowka, Wydział nżynieii Elektycznej i Komputeowej, ntytut Elektomechanicznych Pzemian Enegii, ul. Wazawka 24, Kaków. PRZEGLĄD ELEKTROTECHNCZNY Electical Review), SSN , R. 87 NR 5/